CVE-2026-72421

Network-path denial via overwritten error routes

Published Aug 15, 2026 · Updated Aug 15, 2026

Improper error handling in the Linux kernel IPv4 FIB allows local users to disrupt network routing under specific policy settings. When CONFIG_IP_MULTIPLE_TABLES is enabled without added rules, fib_lookup() continues after an error-route result and overwrites it with a default-table route. A local user with sufficient routing control can make traffic follow a route that an unreachable entry should reject, causing inconsistent or unavailable network paths.

CVSS severity5.5
Medium
EPSS probability0.57%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper error handling in the Linux kernel IPv4 FIB allows local users to disrupt network routing under specific policy settings. When CONFIG_IP_MULTIPLE_TABLES is enabled without added rules, fib_lookup() continues after an error-route result and overwrites it with a default-table route. A local user with sufficient routing control can make traffic follow a route that an unreachable entry should reject, causing inconsistent or unavailable network paths.

The record

CVE
CVE-2026-72421
Published
Aug 15, 2026
Updated
Aug 15, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-390
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 15, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.6
  2. Affected versionversion=f4530fa574df4d833506c53697ed1daa0d390bf4 <49eaf1403201357762d745a35882fb734107d763
  3. Affected versionversion=f4530fa574df4d833506c53697ed1daa0d390bf4 <5ae18d87a45698e8244d0fcba64c658c35a7dd3d
  4. Affected versionversion=f4530fa574df4d833506c53697ed1daa0d390bf4 <828fad4fd418bcdb9f5d66fec0d184c52a85ec31
  5. Affected versionversion=f4530fa574df4d833506c53697ed1daa0d390bf4 <9127589aabdee588278e8d0d0bd3709a760a92c8
  6. Affected versionversion=f4530fa574df4d833506c53697ed1daa0d390bf4 <a29e95fbc51e8a1b932773fd0e259b2080881443
  7. Affected versionversion=f4530fa574df4d833506c53697ed1daa0d390bf4 <a668fa160247d7bbe921548cb845f607b8b9305f
  8. Affected versionversion=f4530fa574df4d833506c53697ed1daa0d390bf4 <b72f0db64205d9ce462038ba995d5d31eff32dc1
  9. Affected versionversion=f4530fa574df4d833506c53697ed1daa0d390bf4 <fd25996f57a95d56bc568c89b4921edcf334b7d8

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3.6; version=f4530fa574df4d833506c53697ed1daa0d390bf4 <49eaf1403201357762d745a35882fb734107d763; version=f4530fa574df4d833506c53697ed1daa0d390bf4 <5ae18d87a45698e8244d0fcba64c658c35a7dd3d; version=f4530fa574df4d833506c53697ed1daa0d390bf4 <828fad4fd418bcdb9f5d66fec0d184c52a85ec31; version=f4530fa574df4d833506c53697ed1daa0d390bf4 <9127589aabdee588278e8d0d0bd3709a760a92c8; version=f4530fa574df4d833506c53697ed1daa0d390bf4 <a29e95fbc51e8a1b932773fd0e259b2080881443; version=f4530fa574df4d833506c53697ed1daa0d390bf4 <a668fa160247d7bbe921548cb845f607b8b9305f; version=f4530fa574df4d833506c53697ed1daa0d390bf4 <b72f0db64205d9ce462038ba995d5d31eff32dc1; version=f4530fa574df4d833506c53697ed1daa0d390bf4 <fd25996f57a95d56bc568c89b4921edcf334b7d8

Published CVSS scores

3.3Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
5.5Red HatCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5Oracle LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-390Detection of Error Condition Without Action

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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